Zoom lens and imaging apparatus

Abstract

A zoom lens consists of, in order from an object side to an image side: an object side positive group which has a positive refractive power; an object side negative group which has a negative refractive power; an intermediate group; and a final group. The object side positive group, the object side negative group, the intermediate group, and the final group each include at least one lens group. All spacings between adjacent lens groups change, and all mutual spacings between lenses in each lens group do not change during zooming. All lenses in the object side positive group and all lenses in the intermediate group remain stationary with respect to an image plane during focusing. The zoom lens satisfies predetermined conditional expressions.

What is claimed is: 
     
         1 . A zoom lens consisting of, in order from an object side to an image side:
 an object side positive group which has a positive refractive power;   an object side negative group which has a negative refractive power;   an intermediate group; and   a final group,   wherein the object side positive group, the object side negative group, the intermediate group, and the final group each include at least one lens group,   all spacings between adjacent lens groups change, and all mutual spacings between lenses in each lens group do not change during zooming,   all lenses in the object side positive group and all lenses in the intermediate group remain stationary with respect to an image plane during focusing, and   assuming that
 a back focal length of the zoom lens in terms of an air-equivalent distance in a state where an infinite distance object is in focus at a wide-angle end is βfw, 
 a focal length of the zoom lens in the state where the infinite distance object is in focus at the wide-angle end is fw, and 
 a maximum half angle of view in the state where the infinite distance object is in focus at the wide-angle end is ωw, 
 Conditional Expression (1) is satisfied, which is represented by 
   
       
         
           
             
               
                 
                   
                     0.5 
                     < 
                     
                       Bfw 
                       / 
                       
                         ( 
                         
                           fw 
                           × 
                           tan 
                           ⁢ 
                           ω 
                           ⁢ 
                           w 
                         
                         ) 
                       
                     
                     < 
                     5. 
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
     
     
         2 . The zoom lens according to  claim 1 , wherein the object side negative group includes a lens group, which is closest to the object side and which has a negative refractive power, among the lens groups which have negative refractive powers and which are included in the zoom lens. 
     
     
         3 . The zoom lens according to  claim 1 , wherein the final group consists of one lens group. 
     
     
         4 . The zoom lens according to  claim 1 , wherein the intermediate group includes at least three lenses. 
     
     
         5 . The zoom lens according to  claim 1 , wherein assuming that
 a paraxial curvature radius of an object side surface of a negative lens, which is closest to the object side, among the negative lenses, which are included in the object side negative group, is Rnf, and   a paraxial curvature radius of an image side surface of the negative lens, which is closest to the object side, among the negative lenses, which are included in the object side negative group, is Rnr,   Conditional Expression (2) is satisfied, which is represented by   
       
         
           
             
               
                 
                   
                     0.02 
                     < 
                     
                       
                         ( 
                         
                           Rnf 
                           - 
                           Rnr 
                         
                         ) 
                       
                       / 
                       
                         ( 
                         
                           Rnf 
                           + 
                           Rnr 
                         
                         ) 
                       
                     
                     < 
                     3. 
                   
                 
                 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     
         6 . The zoom lens according to  claim 1 , wherein during zooming, a lens group, which is closest to the object side in the object side positive group, moves. 
     
     
         7 . The zoom lens according to  claim 1 , comprising at least one focusing group that moves during focusing,
 wherein a focusing group, which is closest to the object side, among the focusing groups, which are included in the zoom lens, has a negative refractive power.   
     
     
         8 . The zoom lens according to  claim 1 ,
 wherein the object side negative group includes at least two negative lenses,   an image side surface of a negative lens, which is closest to the object side, among the negative lenses, which are included in the object side negative group, is a concave surface, and   an object side surface of a negative lens, which is closest to the image side, among the negative lenses, which are included in the object side negative group, is a concave surface.   
     
     
         9 . The zoom lens according to  claim 1 ,
 wherein the intermediate group includes at least one lens group which has a positive refractive power,   a lens group, which is closest to the object side and which has a positive refractive power, among lens groups, which are included in the intermediate group and which have positive refractive powers, includes at least two positive lenses, and   assuming that
 an Abbe number of a positive lens, which is closest to the object side, among positive lenses, which are included in the intermediate group, based on a d-line is vMp1, and 
 an Abbe number of a positive lens, which is second from the object side, among the positive lenses, which are included in the intermediate group, based on the d-line is vMp2, 
 Conditional Expression (3) is satisfied, which is represented by 
   
       
         
           
             
               
                 
                   
                     20 
                     < 
                     
                       
                         ( 
                         
                           
                             vMp 
                             ⁢ 
                             1 
                           
                           + 
                           
                             vMp 
                             ⁢ 
                             2 
                           
                         
                         ) 
                       
                       / 
                       2 
                     
                     < 
                     100. 
                   
                 
                 
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
     
         10 . The zoom lens according to  claim 1 , wherein the intermediate group includes at least two lens groups in which a spacing between adjacent lens groups changes during zooming. 
     
     
         11 . The zoom lens according to  claim 1 ,
 wherein the intermediate group includes at least one lens group which has a positive refractive power, and   a lens group, which is closest to the object side and which has a positive refractive power, among lens groups, which have positive refractive powers and which are included in the intermediate group, includes two positive lenses, successively in order from a position closest to the object side to the image side.   
     
     
         12 . The zoom lens according to  claim 1 ,
 wherein the intermediate group includes at least one lens group which has a positive refractive power,   a lens group, which is closest to the object side and which has a positive refractive power, among lens groups, which are included in the intermediate group and which have positive refractive powers, includes at least two positive lenses, and   an object side surface of a positive lens, which is closest to the object side, among the positive lenses, which are included in the lens group that is closest to the object side and that has a positive refractive power in the intermediate group, is a convex surface.   
     
     
         13 . The zoom lens according to  claim 1 , wherein the object side negative group includes at least four lenses. 
     
     
         14 . The zoom lens according to  claim 1 , wherein assuming that an open F number in a state where the infinite distance object is in focus at the wide-angle end is Fnow, Conditional Expression (4) is satisfied, which is represented by 
       
         
           
             
               
                 
                   
                     2 
                     < 
                     Fnow 
                     < 
                     
                       4.8 
                       . 
                     
                   
                 
                 
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
     
     
         15 . The zoom lens according to  claim 1 , wherein a lens group closest to the image side among lens groups that are included in the intermediate group has a positive refractive power. 
     
     
         16 . The zoom lens according to  claim 1 , wherein assuming that a focal length of the object side positive group at the wide-angle end is fGPw, Conditional Expression (5) is satisfied, which is represented by 
       
         
           
             
               
                 
                   
                     0.05 
                     < 
                     
                       fw 
                       / 
                       fGPw 
                     
                     < 
                     
                       2.5 
                       . 
                     
                   
                 
                 
                   
                     ( 
                     5 
                     ) 
                   
                 
               
             
           
         
       
     
     
         17 . The zoom lens according to  claim 1 , wherein assuming that
 a focal length of the zoom lens in a state where the infinite distance object is in focus at a telephoto end is ft, and   a focal length of the object side positive group at the wide-angle end is fGPw,   Conditional Expression (6) is satisfied, which is represented by   
       
         
           
             
               
                 
                   
                     0.4 
                     < 
                     
                       ft 
                       / 
                       fGPw 
                     
                     < 
                     
                       4.5 
                       . 
                     
                   
                 
                 
                   
                     ( 
                     6 
                     ) 
                   
                 
               
             
           
         
       
     
     
         18 . The zoom lens according to  claim 1 , wherein the object side negative group includes a lens group in which a biconvex air lens is formed. 
     
     
         19 . The zoom lens according to  claim 1 ,
 wherein the object side negative group includes a lens group which has a negative refractive power, and   the entirety or a part of the lens group which has the negative refractive power in the object side negative group moves along an optical axis during focusing.   
     
     
         20 . The zoom lens according to  claim 1 , wherein the entirety or a part of the final group moves along an optical axis during focusing. 
     
     
         21 . The zoom lens according to  claim 1 , wherein a lens group closest to the image side in the final group moves during zooming. 
     
     
         22 . An imaging apparatus comprising: the zoom lens according to  claim 1 .